Most telephone operating companies have an infrastructure of twisted-pair copper wire (also referred to as tip-ring pairs) connecting a telephone at a customer premise to a switching office. While this has been adequate for voice service for over a hundred years, modern data technologies are taxing the bandwidth limitations of twisted-pair service. Some operating companies are experimenting with fiber optic to the home, cable television (CATV) equipment, etc., in order to increase bandwidth for home and business use. These technologies are expensive to the operating companies because they require the operating company to physically rewire an entire community from each customer premise to a local switching office.
One new data service technology that takes advantage of the currently extant twisted-pair infrastructure is digital subscriber line (DSL). DSL comes in many varieties, such as asynchronous DSL (ADSL) and synchronous DSL (SDSL), each having further “flavors”. The advantage of DSL is that it may be implemented over the current tip-ring pair infrastructure and, with some DSL systems, the current customer premise telephone equipment may be used. Increasingly, voice communication from a customer premise is viewed as one more payload for the DSL. Therefore, voice over DSL-(VoDSL) is proposed as a method of more fully utilizing the bandwidth of the twisted pair. An integrated access device is used on the customer premise to integrate voice service over the data service.
One issue that each DSL service provider must face is how the customer premise integrated access device is to be powered. In POTS telephony, 48 volts DC is supplied from the central office for most functions, and approximately 90 volts AC is supplied from the central office for ringing. The integrated access device must supply these voltages to all POTS telephones to which it is connected; as well as supply power to the other components (interfaces, routers, etc., as will be discussed further, below, in connection with FIG. 2). Some DSL standards specify that power is delivered from the central office in a similar manner as POTS service. However, the integrated access device requires power at all times, and requires more power than a POTS telephone. Thus, central power delivery is a very expensive proposition for the operating company. Hence, most integrated access devices are powered from the consumer power company (wherein the customer pays for the power).
One issue with VoDSL when power is provided by the power company is that, if the power goes out at the consumer premise, the customer can no longer use either the data terminal or, more importantly, the telephones. This is a problem in the art in that many regulatory agencies require emergency (911) service (“lifeline service”) even during periods of power outages.
An obvious solution is to use a battery backup at the integrated access device. This solution, however, causes as many problems as it solves. In normal operation, an integrated access device does not use the batteries and the user does not know (or care) whether the batteries are fully charged or not. Only when the power goes out does the user determine whether the batteries are charged. Such a situation is not acceptable to most regulatory agencies. Battery monitoring by the operating company is generally required. However, this monitoring usually includes sending crafts people to the customer premise to replace batteries, etc. which is the most expensive method of monitoring anything.
Therefore, a problem in the art is that there is no reliable backup system or method for providing power for lifeline service to commercially powered voice over DSL customers.